Methods and apparatus for cell selection/reselection in millimeter wave system

ABSTRACT

Methods and apparatus for cell selection, cell reselection, and beam selection in MMW system are provided. The UE measures signal strength, or signal quality or both of them to get the best consolidation measurement result. During Cell Selection, the UE selects the cell with the best consolidation measurement result, or selects the cell containing the candidate control beam found firstly. In Cell Reselection, the serving cell and neighboring cells are ranked based on the consolidation measurement result. After camping on a cell, the UE selects one or more than one best control beams as the serving control beam to acquire system information and monitor paging message. Furthermore, the UE selects the best control beam or selects one control beam randomly among the serving control beams to initial access to the network.

TECHNICAL FIELD

The disclosed embodiments relate generally to wireless communication, and, more particularly, to cell selection and cell reselection in a millimeter wave system.

BACKGROUND

The bandwidth shortage increasingly experienced by mobile carriers has motivated the exploration of the underutilized millimeter wave (mmW) frequency spectrum between 3 G and 300 G Hz for the next generation broadband cellular communication networks. The available spectrum of mmW band is two hundred times greater than the conventional cellular system. The mmW wireless network uses directional communications with narrow beams and can support multi-gigabit data rate. The underutilized bandwidth of the mmW spectrum has wavelengths ranging from 1 mm to 100 mm. The very small wavelengths of the mmW spectrum enable large number of miniaturized antennas to be placed in a small area. Such miniaturized antenna system can produce high beamforming gains through electrically steerable arrays generating directional transmissions.

With recent advances in mmW semiconductor circuitry, mmW wireless system has become a promising solution for the real implementation. However, the heavy reliance on directional transmissions present particular challenges for the mobile stations in the mmW network, such as cell selection and cell reselection procedures during IDLE mode. Unlike the traditional cellular system, one mmW cell is covered by one or more than one directional beams. Therefore, the synchronization and broadcast signals for a cell are also directional and only cover a small area. The mobile stations need to san over a range of angles before a cell can be detected. The time latency would be even longer in standalone mmW system due to the lack of assistance information from the network. The frequent execution of finding a narrow beam to camp on during mobile movement is more complicated with more power consumption for measurement.

Improvements and enhancements are required for cell selection and cell reselection in the mmW network.

SUMMARY

Methods and apparatus are provided for cell selection, cell reselection and beam selection in mmW system. In one novel aspect, consolidation measurements are used for cell selection and cell reselection for a UE in the mmW system. The UE measures signal strength, signal energy/power, signal quality, signal lifetime, signal error rate, signal angle of arrival (AoA)/direction of arrival (DoA) or a combination of the above to get the best consolidation measurement result. In one embodiment, the UE selects a set of control beams for each cell as qualified control beam to obtain the consolidation measurement. In one embodiment, the set of qualified control beams are multiple detected control beams associated with the cell. In another case, the set of qualified control beams are all the detected control beams associated with the cell. In another embodiment, the set of qualified control beams are multiple candidate control beams associated with the cell, where the candidate control beams is a subset of the detected control beams meeting a predefined criterion. In yet other embodiments, different consolidation rules are used to obtain the consolidation measurement.

In another novel aspect, during cell selection, the UE selects the cell with the best consolidation measurement result, or selects the cell containing the candidate control beam found firstly. In another embodiment, the UE selects one or more control serving beams from the control beams of the serving cell. The UE receives control information and system information on the serving control beams. In another embodiment, the UE selects an access control beam from the selected serving control beam(s) to initiate RRC connection.

In yet another novel aspect, during cell reselection, the serving cell and neighboring cells are ranked based on the consolidation measurement result. In one embodiment, the UE compares the serving-cell consolidation measurement with a set of measurement thresholds. The UE determines the measurement level based on the comparison. The measurement level includes measuring the serving control beams of the serving cell, measuring the serving and non- serving control beams of the serving cell, measuring the neighboring cells with the same frequency, and measuring the neighboring cells with different frequencies.

In one novel aspect, after the UE camps on a cell, the UE selects one or more than one best control beams as the serving control beam(s) to acquire system information and monitor paging message. Furthermore, the UE selects the best control beam or selects one control beam randomly among the serving control beams to initial access to the network.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, where like numerals indicate like components, illustrate embodiments of the invention.

FIG. 1 is a schematic system diagram illustrating an exemplary wireless network with mmW connections in accordance with embodiments of the current invention.

FIG. 2 shows an exemplary flow chart of a UE performing cell selection and cell reselection in the IDLE mode in the mmW system.

FIG. 3 illustrates an exemplary control beam configuration for UL and DL of the UE in accordance with the current invention.

FIG. 4 shows an exemplary flow chart for a cell selection in mmW system in accordance with embodiments of the current invention.

FIG. 5 illustrates an exemplary table that shows the consolidation measurement results based on different consolidation rules/methods in accordance with embodiments of the current invention.

FIG. 6 illustrates exemplary flow charts of consolidation measurements performed for serving cells and neighbor cells for the cell reselection in the mmW system.

FIG. 7 shows an exemplary flow chart of the UE performing cell reselection measurement based on measurement rules according to a set of threshold in accordance with embodiments of the current invention.

FIG. 8 illustrates different sets of control beam selections for the UE measurement for cell reselection in accordance with embodiments of the current invention.

FIG. 9 shows an exemplary flow chart for the cell reselection process in the mmW system in accordance with embodiments of the current invention.

FIG. 10 illustrates an exemplary flow chart for beam selection for the UE in the mmW system in accordance with embodiments of the current invention.

FIG. 11 is an exemplary flow chart for obtaining the consolidation measurement of each cell by the UE in the mmW system.

FIG. 12 is an exemplary flow chart for cell selection process of the UE in the mmW system in accordance with embodiments of the current invention.

FIG. 13 is an exemplary flow chart for cell reselection process of the UE in the mmW system in accordance with embodiments of the current invention.

DETAILED DESCRIPTION

Reference will now be made in detail to some embodiments of the invention, examples of which are illustrated in the accompanying drawings.

FIG. 1 is a schematic system diagram illustrating an exemplary wireless network 100 with mmW connections in accordance with embodiments of the current invention. Wireless system 100 includes one or more fixed base infrastructure units forming a network distributed over a geographical region. The base unit may also be referred to as an access point, an access terminal, a base station, a Node-B, an eNode-B, or by other terminology used in the art. As an example, base stations 101, 102 and 103 serve a number of mobile stations 104, 105, 106 and 107 within a serving area, for example, a cell, or within a cell sector. In some systems, one or more base stations are communicably coupled to a controller forming an access network that is communicably coupled to one or more core networks. eNB 101 is a conventional base station served as a macro eNB. eNB 102 and eNB 102 are mmW base stations, whose serving area partially or wholly overlap with the serving area of eNB 101, or does not overlap, as well as at least partially overlap with each other at the edge. mmW eNB 102 and mmW eNB 103 has multiple sectors each with multiple control beams to cover a directional area, wherein each control beam further comprises multiple dedicated beams in hierarchy. Control beams 121, 122, 123 and 124 are exemplary control beams of eNB 102. Control beams 125, 126, 127 and 128 are exemplary control beams of eNB 103. As an example, UE or mobile station 104 is only in the service area of eNB 101 and connected with eNB 101 via a link 111. UE 106 is connected with mmW network only, which is covered by control beam 124 of eNB 102 and is connected with eNB 102 via a link 114. UE 105 is the overlapping service area of eNB 101 and eNB 102. In one embodiment, UE 105 is configured with dual connectivity and can be connected with eNB 101 via a link 113 and eNB 102 via a link 115. UE 107 is in the service areas of eNB 101, eNB 102 and eNB 103. During cell selection in the mmW system, UE 107 measures multiple cells covered by eNB 102 and eNB 103. Each of mmW cells has one or more control beams. UE 107 measures the detected beams and calculates a consolidation measurement for each cell. In one embodiment, UE 107 performs cell selection and cell reselection based on consolidation measurements for each cell.

FIG. 1 further illustrates simplified block diagrams 130 and 150 for UE 107 and eNB 103, respectively. Mobile station 107 has an antenna 135, which transmits and receives radio signals. A RF transceiver module 133, coupled with the antenna, receives RF signals from antenna 135, converts them to baseband signals, and sends them to processor 132. RF transceiver module 133 is an example, and in one embodiment, the RF transceiver module comprises two RF modules (not shown), first RF module is used for mmW transmitting and receiving, and another RF module is used for different frequency bands transmitting and receiving, which is different from the mmW transceiving. RF transceiver 133 also converts received baseband signals from processor 132, converts them to RF signals, and sends out to antenna 135. Processor 132 processes the received baseband signals and invokes different functional modules to perform features in mobile station 107. Memory 131 stores program instructions and data 134 to control the operations of mobile station 107. Mobile station 107 also includes multiple function modules that carry out different tasks in accordance with embodiments of the current invention. A control-beam selection module 141 selects a set of control beams for a cell to obtain the consolidation measurement. A consolidate measurement module 142 calculates the consolidation measurement based on the selected set of control beams and a consolidation rule. A cell selection module 143 performs cell selection for UE 107 in the mmW system. A cell reselection module 144 performs cell reselection for UE 107 in the mmW system. Beam selection module 145 selects a set of serving control beams for UE 107.

Similarly, eNB 103 has an antenna 155, which transmits and receives radio signals. A RF transceiver module 153, coupled with the antenna, receives RF signals from antenna 155, converts them to baseband signals, and sends them to processor 152. RF transceiver module 153 is an example, and in one embodiment, the RF transceiver module comprises two RF modules (not shown), the first RF module is used for mmW transmitting and receiving, and another RF module is used for different frequency bands transmitting and receiving which is different from the module used for mmW. RF transceiver 153 also converts received baseband signals from processor 152, converts them to RF signals, and sends out to antenna 155. Processor 152 processes the received baseband signals and invokes different functional modules to perform features in eNB 103. Memory 151 stores program instructions and data 154 to control the operations of eNB 103. eNB 103 also includes multiple function modules that carry out different tasks in accordance with embodiments of the current invention. An mmW handler 161 handles mmW functions for eNB 103.

FIG. 1 further shows functional procedures that handle cell selection and cell reselection procedures in the mmW system. UE 105 has a consolidation measurement procedure 191 that processes consolidation measurement for UE 105. UE 105 also has cell selection procedure 192 that performs cell selection functions for UE 105 in the mmW system. A cell reselection procedure 193 of UE 105 performs cell reselection functions in the mmW system.

FIG. 2 shows an exemplary flow chart of a UE performing cell selection and cell reselection in the IDLE mode in the mmW system. After the UE powers on or returns to RRC_IDLE from RRC_CONNECTED at step 200, the UE in the IDLE mode transits from three processes, a cell selection process 201, a beam selection/camp-on process 202 and a cell reselection 203. At the top level, upon the UE powers on or returns to RRC_IDLE from RRC_CONNECTED, the UE starts cell selection at step 210. If upon completion of cell selection 210, the UE moves step 220 to camp on the selected cell, which is also called as serving cell. The UE continues monitors the signal strength in the serving cell as well as neighboring cells if needed. The UE moves step 230 to perform cell reselection. Upon completion of the cell reselection, the UE moves back to step 220 to camp on the serving cell.

In connected mode, consolidation measurements could be used for handover. In one embodiment, in idle mode, consolidation measurements are used for cell selection in the mmW system. When the UE starts cell selection, at step 211 the UE obtains signal measurements for multiple cells consisting of multiple control beams. The UE in the mmW system detects multiple control beams associated with one or more mmW cells. The signal measurement can signal strength, signal energy, signal power, signal quality, signal lifetime, signal error rate, signal AoA, or signal DoA. The signal measurement for each control beam can also be any combination of the above or other related measurements that can be obtain to indicate the control beam status. Based on the measurement, the UE can determine a set of candidate control beams of each cell of multiple cells. The candidate control beams are the subset of the detected control beams that meets a predefined criterion. For example, a candidate control beam is a candidate control beam whose signal measurement is greater than a predefine threshold. At step 212, the UE obtains the consolidation measurement results for each cell. The consolidation measurement result for each cell is to computes the measurement results based on a set of signal measurements of one or more control beams associated with the cell. At step 213, the UE applies cell selection criterion based on the obtained consolidation measurement results. At step 214, the UE performs cell selection and selects a cell to camp on.

Unlike traditional cellular system, once camped on a cell, the UE needs to perform beam selection in the serving cell. At step 221, the UE selects one or more serving control beams. The serving control beams are control beams in the serving cell on which the UE acquires system information, receives paging messages, and/or initial access to the network. The serving control beams are a subset of the candidate control beams of the serving cell. There can be one or more serving control beams for the UE. At step 222, the UE acquires system information through the serving control beams. At step 223, the UE monitors the paging message via the serving control beams. At step 224, the UE further selects the access control beam in the serving control beams. The access control beam is a serving control beam that meets a predefined criterion. For example, the access control beam is the serving control beam that has the best signal measurement. In another embodiment, the UE can randomly select one serving control beam as the access control beam.

The UE performs cell reselection in the IDLE state. At step 231, the UE performs priority selection. The UE prioritize different mmW frequencies or inter-RAT (radio access technology) frequencies. In one embodiment, the UE receives the priority configuration information in the dedicated message when the UE release RRC connection, or inherits from another RAT at inter-RAT cell selection or cell reselection. In another embodiment, the UE capable of supporting both EUTRAN and mmW will always consider the EUTRAN frequency as highest priority frequencies. At step 232, the UE obtains consolidation measurement results for the serving cell. At step 233, the UE applies the measurement rules based on the obtained serving cell consolidation-measurement result. If at step 233, the UE determines that neighbor cell measurement is need, the UE moves to step 234. At step 234, the UE measures neighbor cell control beams. At step 235, the UE obtains consolidation measurement results for multiple cells. At step 236, the UE applies cell reselection criterion based on the consolidation measurement results. At step 237, the UE performs cell reselection.

FIG. 3 shows exemplary diagrams and a table illustrating multiple control beam measurement of UE in a mmW network. A UE 303 locates in an area served by with an mmW eNB 301 and mmW eNB 302. eNB 301 and eNB 302 are directionally configured with multiple sectors/cells. Each sector/cell is covered by a set of coarse TX control beams. In one example, three sectors/cells are configured, each covering a 120° sector. In one embodiment, each cell is covered by eight control beams. Different control beams are time division multiplexed and distinguishable. Phased array antenna is used to provide moderate beamforming gain. The set of control beams is transmitted repeatedly and periodically. Each control beam broadcasts the cell-specific information such as synchronization signal, system information, and beam-specific information.

As an example, eNB 301 covers three cells #0 and cell #1 and cell #2. Similarly, eNB 302 covers three cells #3 and cell #4 and cell #5. UE 303 detects control beams for cell selection. As an example shown in FIG. 3, each cell is configured with eight control beams. UE 303 detects multiple control beams and performs signal measurements on the detected multiple control beams. Up detecting control beams, UE 303 may determine whether the detected control beam is a candidate control beam based on a candidate rule. In one embodiment, the detected control beam is a candidate control beam if the signal measurement is larger than a threshold. As an example, FIG. 3 illustrates a table 300 of detected control beams and candidate control beams for UE 303. A list of control beams is listed for each cell in a descending order of the signal measurement. UE 303 detects control beams (CBs) CB8, CB7, CB6 and CB3 in descending order from cell #0. UE 303 determines that CB8, CB7, and CB6 are candidate control beams from cell #0. Similarly, UE 303 detects control beams CB2, CB1 and CB4 in descending order from cell #1. UE 303 determines that CB2, and CB1 are candidate control beams from cell #1. For Cell #2, UE 303 detects control beams CB8 and CB7 and determines that CB8 is the candidate control beam. UE 303 detects control beams CB2, CB1, CB3 and CB6 in descending order from cell #3. UE 303 determines that CB2, CB1, and CB3 are candidate control beams from cell #3. Once the UE detects control beams and determines candidate control beams, the UE calculates the consolidation measurement for each cell based on the one or more signal measurement obtained associated with the corresponding cell.

FIG. 4 shows an exemplary flow chart for a cell selection in mmW system in accordance with embodiments of the current invention. At step 401, the UE detects control beams and performs signal measurement for each detected control beam. At step 402, the UE determines whether the control beam is a candidate control beam. In one embodiment, the UE compares the signal measurement of the control beam with a predefined threshold to determine if the signal measurement is larger than the threshold. If step 402 determines no, the control beam is only a detected control beam at step 403. If step 402 determines yes, the control beam is considered as a candidate control beam at step 404. Steps 402, 403 and 404 are optional. In some embodiments, the UE takes consolidation measurement based on detected control beams for each cell and steps 402, 403 and 404 are skipped. In another embodiment, upon detecting the first candidate control beam at step 402, the UE selects the first found associated cell as the serving cell. In other embodiments, the UE moves to step 405 to determine which set of control beams should be used for consolidation measurement for each cell. In one embodiment, all detected control beams are used. In the second embodiment, multiple control beams of all detected control beams are used. In the third embodiment, only candidate control beams are used, or part of the candidate control beams of all the candidate control beams are used. In the fourth embodiment, the UE can select other sets of control beams for each cell based on qualified-control-beam rules.

Once the UE selected the set of qualified control beams for consolidation measurement, the UE moves to step 411 wherein the UE obtains consolidation measurement for each cell. The UE obtains the consolidation measurement based on a consolidation rule 421. The consolidation rule can be configured or predefined. Different consolidation rules can be used. Each applied to the selected set of qualified control beams associated with the cell as determined in step 405. In one embodiment (method #1), the resulting consolidation measurement of the set of qualified control beams of the cell is the number of qualified control beams in the set. In other embodiments the resulting consolidation measurement of the set of qualified control beams of the cell is the maximum signal measurement of the set (method #2), or the minimum signal measurement of the set (method #3), or the mean value of signal measurements of the set (method #4), or the variance of signal measurements of the set (method #5), or the sum of the signal measurements of the set (method #6). Other consolidation methods can be used. In other embodiments, a combination of different methods may be used, for example, a combination of method #1 and method #2.

Once the consolidation measurements is determined for each cell, the UE moves to step 412 and finds the cell with the best consolidation result following a cell selection rule 422. Examples of the cell selection rule 422 includes determining the best cell being the cell whose consolidation measurement has the largest number of qualified control beams in the set, or has the largest maximum signal measurement of the set, or has the largest minimum signal measurement of the set, or has the largest mean value of signal measurements of the set, or has the smallest variance of signal measurement of the set, or has the largest sum of signal measurements of the set. Other cell selection rules can be used or combinations of the cell selection rules can be used.

Upon successfully selecting a serving cell, the UE moves to step 413 and finds one or more serving control beams of the serving cell using a beam selection rule 423. The UE receives control and signal information on the selected serving control beams.

FIG. 5 illustrates an exemplary table that shows the consolidation measurement results based on different consolidation rules/methods in accordance with embodiments of the current invention. A table 500 lists the resulting consolidation measurement rules/methods assuming the detecting control beams shown in table 300 of FIG. 3. Table 500 assumes that candidate control beams are selected as qualified control beams for the consolidation measurement. Using method #1, Cell #0 has 3CBs, Cell #1 has 2CBs, Cell #2 has 1CB, and Cell #3 has 3CB. Similarly, the UE can use different consolidation method as listed in table 500 to get a consolidation measurement for the corresponding cells. The resulting consolidation measurement for each cell can be the maximum signal measurement of the CB of the set (method #2), or the minimum signal measurement of the CB of the set (method #3), or the mean value of measurements of all candidate CBs of the set (method #4), or the variance of measurement of all candidate CBs of the set (method #5), or the sum of the measurements of all candidate CBs of the set (method #6).

In other embodiments, combinations of the above methods are used for the signal measurement of each cell. For example, the signal measurement results for each cell contains two measurements: a first weighted resulting consolidation measurement for each cell is the maximum signal measurement of the CB of the set (method #2) and a second weighted resulting consolidation measurement for each cell is the number of qualified control beams (method #1). The ranking of cells may be the same or may be different based on different measurements contained in the signal measurement. Providing a combination signal measurement for each cell presents a more complete picture of the cell condition such that the UE can select a better cell for cell selection, cell reselection, and/or handover. For example, using method #2, cell #2 may rank higher than cell #0 with a slightly higher maximum signal strength. However, using method #1, cell #0 may rank higher than cell #2 with a higher number of candidate control beams. In one embodiment, the UE uses an algorithm to select the target cell for cell selection, cell reselection, and/or handover. For example, a signal threshold is set such that the best-ranked cell using method #2 is selected if the maximum signal measurement is greater than the signal threshold; otherwise, the best-ranked cell using method #1 is selected. Similarly, a number threshold is set such that the best-ranked cell using method #1 is selected if the number of qualified control beams is greater than the number threshold; otherwise, the best-ranked cell using method #2 is selected. In other embodiments, a set of thresholds and/or a combination of thresholds are used for cell ranking Multiple signal measurements can be combined with corresponding cell ranking algorithms.

FIG. 6 illustrates exemplary flow charts of consolidation measurements performed for serving cells and neighbor cells for the cell reselection in the mmW system. At step 601, the UE determines a set of qualified control beams for consolidation measurement for the serving cell. For example, the set of qualified control beams may be the detected control beams in the serving cell, or the candidate control beams of the serving cell or the serving control beams of the serving cell. At step 602, the UE calculates the consolidation measurement for the serving cell based on the control beam selection at step 601. At step 603, the UE obtains the serving cell consolidation-measurement result RES_S. Similarly, the UE At step 611, the UE determines a set of qualified control beams for consolidation measurement for the neighboring cells. For example, the set of qualified control beams may be the detected control beams in the neighbor cells, or the candidate control beams of the neighboring cells. At step 612, the UE calculates the consolidation measurement for the neighboring cells based on the set of qualified control beams at step 611. At step 613, the UE obtains the neighboring cells consolidation-measurement result RES_N.

In the mmW system, the UE needs to monitor multiple beams in a cell to obtain the measurement result. The power consumption is a concern for frequent measurement. In one embodiment for cell reselection, the UE determines the set of control beams to measure based on a comparison between the consolidation measurement result of the serving cell and a set of thresholds. FIG. 7 shows an exemplary flow chart of the UE performing cell reselection measurement based on measurement rules according to a set of threshold in accordance with embodiments of the current invention. In one embodiment, the UE is configured with a set of measurement thresholds, Threshold_1, Threshold_2, and Threshold_3 in a descending order. Threshold_1 is defined for intra-cell measurement. Threshold_2 is defined for intra-frequency measurements. Threshold_3 is defined for inter-frequency and inter-RAT measurements. Threshold_1 can be broadcasted in the system information or beam-specific information.

Threshold_2 and Threshold_3 can be broadcasted in the system information.

At step 701, the UE compares the serving cell consolidation measurement RES_S, as shown in FIG. 6, with a set of thresholds. At step 702, the UE determines if RES_S is smaller than Threshold_3. If step 702 determines yes, the UE moves step 711 of a first measurement level. The UE performs inter-frequency control beams measurement at step 711. If step 702 determines no, the UE moves step 703. At step 703, the UE determines if RES_S is smaller than Threshold_2. If step 702 determines yes, the UE moves step 712 of a second measurement level. The UE performs intra-frequency control beams measurement at step 712, where only the UE measures control beams of neighbor cells with the same frequency as the serving cell. If step 702 determines no, the UE moves step 704. At step 704, the UE determines if RES_S is smaller than Threshold_1. If step 704 determines yes, the UE moves step 713 of a third measurement level. The UE does not measure control beams from neighbor cells. The UE measures non-serving control beams of the serving cell. If step 704 determines no, the UE moves step 714 of a fourth measurement level. At step 714, the UE only measures the serving control beams of the serving cell.

FIG. 8 illustrates different sets of control beam selections for the UE measurement for cell reselection in accordance with embodiments of the current invention. Diagram 801 shows different control beam configurations for the serving cell. The serving cell has a set of control beams. The UE detects multiple control beams in the serving cell, namely detected control beams 811. Candidate control beams 812 is a subset of detected control beam 811. Serving control beams 813 is a subset of candidate control beams 812. For neighbor cells, there is no serving control beam set. Diagram 802 shows different control beam configurations for a neighboring cell. The neighboring cell has a set of control beams. The UE detects multiple control beams in the neighboring cell, namely detected control beams 821. Candidate control beams 822 is a subset of detected control beam 821.

For cell reselection measurement, the UE can use different sets of control beams for serving cell and neighbor cells. FIG. 8 shows an exemplary table 800 of different combinations of measurement the UE can take for cell reselection. Table 800 assumes the measurement of Table 300 as shown in FIG. 3. The UE can use different control beam sets for cell reselection measurement. For example, shown in the first row of Table 800, the UE uses serving control beams for the serving consolidation measurement while using candidate control beams for neighboring cells' consolidation measurements. Shown in the second row of Table 800, the UE uses serving control beams for the serving consolidation measurement while using detected control beams for neighboring cells' consolidation measurements. Similarly, shown in the third row of Table 800, the UE uses candidate control beams for the serving consolidation measurement while using detected control beams for neighboring cells' consolidation measurements. In another embodiment, the UE can use the same set of control beams for the serving cell and the neighboring cells. Both the serving cell and neighboring cells use candidate control beams for the consolidation measurement, as shown in the fourth row of Table 800. Similarly, both the serving cell and neighboring cells use detected control beams for the consolidation measurement, as shown in the fifth row of Table 800.

FIG. 9 shows an exemplary flow chart for the cell reselection process in the mmW system in accordance with embodiments of the current invention. The cell reselection process includes three stages, a stage 910 wherein cells with higher priority frequency are considered, a stage 920 wherein cells with lower priority frequency are considered and a stage 930 wherein the cells with equal priority frequency are considered. At step 911, the UE determines if a cell of higher priority frequency fulfills a predefined condition for cell reselection. If step 911 determines yes, the UE moves to step 912 to check if a timer T1 has elapsed since the UE camped on the current serving cell. If step 912 determines yes, the UE moves to step 913 and performs a cell reselection to a cell of higher priority frequency. If at step 912, the UE determines no, or the UE determines no at step 911, the UE moves out of stage 910 and moves to step 921 of stage 920.

At step 921, the UE determines if a cell of lower priority frequency fulfills a predefined condition for cell reselection. If step 921 determines yes, the UE moves to step 922 to check if a timer Ti has elapsed since the UE camped on the current serving cell. If step 922 determines yes, the UE moves to step 923 and performs a cell reselection to a cell of lower priority frequency. If at step 922, the UE determines no, or the UE determines no at step 921, the UE moves out of stage 920 and moves to step 931 of stage 930.

At step 931, the UE calculates serving cell consolidation measurement results Rs and neighboring cell consolidation measurement results Rn are based on RES_S and RES_N as shown in FIG. 6, respectively. The UE then moves to step 932. At step 932, the ranks of the serving cell and neighboring cells are determined based on Rs and Rn values. At step 933, the UE determines if there exists a new cell better than the current serving cell for a T2 period. If step 933 determines yes, the UE moves to step 934 and determines if the UE has camped on the current serving cell for T1 period. If step 934 determines yes, the UE moves to step 935 and performs cell reselection to the new cell. If step 933 determines no, or step 934 determines no, the UE moves back to step 911.

Upon successful cell selection or cell reselection, the UE in the mmW system needs to select serving control beams. Further, while the UE camps on a serving cell, the UE performs beam selection to select better control beams to be serving control beams. FIG. 10 illustrates an exemplary flow chart for beam selection for the UE in the mmW system in accordance with embodiments of the current invention. At step 1001, the UE performs control beam measurement. At step 1002, the UE obtains the measurement results for each control beam of the serving cell, where the serving control beams have the result denoted as Bmeas_s and none-serving control beam has the measurement of Bmeas_ns. At step 1003, the UE calculates the measurements of serving control beams Bs and none-serving control beams Bns. In one embodiment, the Bs for serving control beams equals to the measured result for the serving beam Bmeas_s plus a hypothesis vale, Q_h while Bn for the none-serving control beams equals to the measurement result of Bmeas_n. Therefore, for the i-th serving control beam, Bs_i=Bmeas_n,i+Q_h. For the j-th none-serving control beam, Bns_j=Bmeas_ns,j. In one embodiment, the Q_h is broadcasted in the system information or beam specific information. At step 1004, the UE ranks the serving control beams and non-serving control beams based on the Bs and Bns. At step 1005, the UE determines if one or more non-serving control beams are better ranked than one or more current serving-control-beams. If step 1005 finds no, the UE moves back to 1001. If step 1005 finds yes, the UE moves to step 1011 and checks if the new control beams have been better ranked for a Tb1 period. If step 1011 finds yes, the UE moves to step 1012 and checks if the current control beams had been used for Tb2 period. If step 1012 finds yes, the UE moves to step 1013 and determines the number N of better-ranked non-serving control beams. At step 1014, the UE replaces the worst N serving control beams with the N better-ranked control beams as the new serving control beams. If step 1011 finds no, or step 1012 finds no, the UE moves to step 1001.

FIG. 11 is an exemplary flow chart for obtaining the consolidation measurement of each cell by the UE in the mmW system. At step 1101, the UE detects multiple control beams in a millimeter wave (mmW) system, wherein the mmW system has multiple cells each configured with multiple control beams. At step 1102, the UE obtains a signal measurement for each detected control beam. At step 1103, the UE calculates a consolidation measurement for each cell based on a set of qualified control beams associated with each corresponding cell using a consolidation rule, wherein at least one cell has more than one associated qualified control beams.

FIG. 12 is an exemplary flow chart for cell selection process of the UE in the mmW system in accordance with embodiments of the current invention. At step 1201, the UE detects multiple control beams of multiple cells in a millimeter wave (mmW) system, wherein the mmW system has multiple cells each configured with multiple control beams. At step 1202, the UE obtains a signal measurement for each detected control beam. At step 1203, the UE performs a cell selection to select a serving cell. At step 1204, the UE selects one or more serving control beams associated with the serving cell, wherein the UE receives control information and system information on the serving control beams.

FIG. 13 is an exemplary flow chart for cell reselection process of the UE in the mmW system in accordance with embodiments of the current invention. At step 1301, the UE obtains a consolidation serving cell measurement for cell reselection (Res_S) in a millimeter wave (mmW) system, wherein the Res_S is calculated based on signal measurements of a set of qualified control beams of the serving cell. At step 1302, the UE determines a measurement level by comparing the Res_S with one or more thresholds in descending order comprising: a first threshold, a second threshold and a third threshold. At step 1303, the UE performs consolidation measurement for one or more cells based on the determined measurement level, wherein the consolidation measurement for a cell is calculated based on signal measurements of a set of control beams associated with the cell. At step 1304, the UE performs a cell reselection based on consolidation measurement results.

Although the present invention has been described in connection with certain specific embodiments for instructional purposes, the present invention is not limited thereto. Accordingly, various modifications, adaptations, and combinations of various features of the described embodiments can be practiced without departing from the scope of the invention as set forth in the claims. 

1. A method comprising: detecting multiple control beams in a millimeter wave (mmW) system by a user equipment (UE), wherein the mmW system has multiple cells each configured with multiple control beams; obtaining a signal measurement for each detected control beam; and calculating a consolidation measurement for each cell based on a set of qualified control beams associated with each corresponding cell using a consolidation rule, wherein at least one cell has more than one associated qualified control beams.
 2. The method of claim 1, wherein the signal measurement of a control beam is obtained based on at least one of the measurements comprising: a signal strength measurement, a signal quality measurement, a signal lifetime measurement, signal error rate, and signal AoA/DoA.
 3. The method of claim 1, wherein the set of qualified control beams of a cell consists of multiple detected control beams associated with the cell.
 4. The method of claim 1, further comprising: determining one or more candidate control beams, wherein the signal measurement of each candidate control beam is greater a candidate threshold.
 5. The method of claim 4, wherein the set of qualified control beams of a cell consists of multiple candidate control beams associated with the cell.
 6. The method of claim 1, wherein the UE is camped on a serving cell and acquires system and control information through one or more serving control beams associated with the serving cell, and wherein the set of qualified control beams for the serving cell consists of multiple serving control beams.
 7. The method of claim 1, wherein the consolidation rule determines the consolidation measurement for the set of qualified control beams is at least one selected from a group comprising: a number of qualified control beams in the set, a maximum signal measurement of the set, a minimum signal measurement of the set, a mean value of signal measurement of the set, a variance of signal measurement of the set, and a sum of the signal measurements of the set.
 8. The method of claim 1, further comprising: performing a cell selection based on consolidation measurement results.
 9. The method of claim 1, further comprising: performing a cell reselection based on consolidation measurement results.
 10. The method of claim 1, further comprising: performing handover based on consolidated measurement results.
 11. A method comprising: detecting multiple control beams in a millimeter wave (mmW) system by a user equipment (UE), wherein the mmW system has multiple cells each configured with multiple control beams; obtaining a signal measurement for each detected control beam; performing a cell selection to select a serving cell; and selecting one or more serving control beams associated with the serving cell, wherein the UE receives control information and system information on the serving control beams.
 12. The method of claim 11, further comprising: determining one or more candidate control beams, wherein the signal measurement of each candidate control beam is greater a candidate threshold.
 13. The method of claim 12, wherein the serving cell is selected upon detecting the first candidate control beam, and wherein the serving cell is the cell that the first detected candidate control beams is associated with.
 14. The method of claim 11, further comprising: calculating a consolidation measurement for each cell based on a set of qualified control beams associated with each corresponding cell using a consolidation rule, wherein at least one cell has more than one associated qualified control beams, and wherein the serving cell is selected based on consolidation measurement results for each cell.
 15. The method of claim 11, wherein the consolidation rule determines the consolidation measurement for the set of qualified control beams is one selected from a group comprising: a number of qualified control beams in the set, a maximum signal measurement of the set, a minimum signal measurement of the set, a mean value of signal measurements of the set, a variance of signal measurement of the set, and a sum of the signal measurements of the set.
 16. The method of claim 11, wherein the selected serving control beams are detected control beams associated with the serving cell.
 17. The method of claim 11, wherein the selected serving control beams are candidate control beams associated with the serving cell, and wherein each candidate control beam has its signal measurement greater than a threshold.
 18. The method of claim 11, wherein the control beams of the serving cell are ranked based on the signal measurement and a predefined number of best control beams of the serving cell are selected based on the ranking as the serving control beams.
 19. The method of claim 11, further comprising: performing a serving control beam selection based on multiple control beam measurements of the serving cell.
 20. The method of claim 19, wherein the serving control beam selection involves: calculating a modified measurement for each serving control beam by adding an hypothesis value to the signal measurement of the corresponding serving control beam; ranking all control beams of the serving cell based on the modified measurement; and selecting one or more best ranked control beams as the new serving control beam candidate.
 21. The method of claim 20, wherein the hypothesis value is obtained and configured by a system information.
 22. The method of claim 20, wherein the hypothesis value is obtained and configured by a beam specific information.
 23. The method of claim 11, further comprising: selecting an access control beam from the one or more selected serving control beams.
 24. A method comprising: obtaining a consolidation serving cell measurement for cell reselection (Res_S) in a millimeter wave (mmW) system by a user equipment (UE), wherein the Res_S is calculated based on signal measurements of a set of control beams of the serving cell; determining a measurement level by comparing the Res _S with one or more thresholds in descending order comprising: a first threshold, a second threshold and a third threshold; and performing consolidation measurement for one or more cells based on the determined measurement level, wherein the consolidation measurement for a cell is calculated based on signal measurements of a set of control beams associated with the cell; and performing a cell reselection based on consolidation measurement results.
 25. The method of claim 24, wherein the signal measurement of a control beam is obtained based on one or more UE measurements comprising: a signal strength measurement, a signal quality measurement, a signal lifetime measurement, signal error rate and signal AoA/DoA.
 26. The method of claim 24, wherein the measurement level is a first level when the Res_S is greater than the first threshold, and wherein the consolidation measurement is only performed for the serving cell based on serving control beams on which the UE receives system and control information.
 27. The method of claim 24, wherein the measurement level is a second level when the Res_S is smaller than the first threshold and larger than the second threshold, and wherein the consolidation measurement is performed on all detected control beams of the serving cell.
 28. The method of claim 24, wherein the measurement level is a third level when the Res_S is smaller than the second threshold and larger than the third threshold, and wherein the consolidation measurement is performed on detected control beams in the serving cell and detected or configured neighbor cell control beams with a same frequency of the serving cell.
 29. The method of claim 24, wherein the measurement level is a fourth level when the Res_S is smaller than the third threshold and wherein the consolidation measurement is performed on all detected control beams of detected control beams in the serving cell and detected or configured neighbor cell control beams with a different frequency of the serving cell. 